In situ bioremediation holds great promise as a safe and cost-effective strategy for cleanup of contaminated sediments and groundwater. The design of bioremediation systems requires site-specific characterization of the types of microorganisms present, what their potential metabolic capabilities are, and to what extent degradative functions are being expressed. The interactions between microbial communities and hazardous wastes also need to be assessed because while microorganisms frequently control both the rate and extent of contaminant metabolism in the subsurface, contaminant mixtures and/or individual mixture components can affect the composition and activity of microbial communities indigenous to contaminated environments.
Laboratory batch and column experiments provide some information about pollutant/microorganism interactions, but cannot reproduce field conditions such as ambient water chemistry, aquifer temperature and the composition of natural microbial communities. Small-scale pilot tests conducted in the field provide better data, but carry the risk of impacting expensive monitoring wells and irretrievably introducing chemical and biological agents into the groundwater.
Previously, capillary microcosms were designed to capture, monitor, and enrich microorganisms in their natural habitat. The device, which can be deployed in a groundwater monitoring well, contains multiple flow-through column microcosms that are packed with site sediment and can be amended with chemical substrates and microorganisms to mimic biostimulation and bioaugmentation treatment approaches. As ambient groundwater is drawn through the capillary microcosms, resident microorganisms are allowed to interact with chemical and biological amendments. All water entering the device is stored in a single effluent container to prevent release of substances into the monitoring well and to enable the calculation of mass balances and biotransformation rates. Upon retrieval of the device from the well, site-specific information becomes available on the effectiveness of each of the treatment strategies tested. Following retrieval from a well, microorganisms are extracted for enumeration and characterization.
Previous methods are described in pending and allowed U.S. patent application Ser. No. 10/797,713, filed Mar. 10, 2004 and entitled “Method and Apparatus for Environmental Monitoring and Bioprospecting,” to the same inventor as the present invention. U.S. patent application Ser. No. 10/797,713 is incorporated herein by reference. The prior method includes the steps of: (a) locating a sampling device in an environment to be investigated, wherein the prior device includes: (i) a container having a fluid inlet and outlet, (ii) a plurality of capillary microcosms situated within the container, each of these capillaries having an inlet and outlet that are configured so as to allow for fluid flow through the capillaries, each of these capillaries further having a means for covering its inlet and outlet so as to prevent flow through the capillary, (iii) a pump connected to the container inlet, the pump being configured so as to draw fluid from the surrounding environment, following which it is forced into the container's inlet and through the capillaries, (iv) connected to the outlet of the container, a means for collecting the flow forced through the capillaries by the pump, and (v) a check valve connected downstream of the container to prevent the backflow of fluid into the container, this plurality of capillaries being configured so as to allow for automated analysis of the capillaries using commercially available robotics, (b) opening the capillary covering means so as to allow fluid from the surrounding environment to flow through the container and capillaries, (c) leaving the device in situ for a temporal duration termed incubation period sufficient to study phenomena occurring within the capillary microcosms, (d) retrieving the testing device, and (e) analyzing phenomena occurring with the capillary microcosms using real-time sensors, automated analysis schemes and commercially available robotics.
Unfortunately, such known methods suffer from several drawbacks. For example, because the pumps are configured to draw fluid through the sampling device it is difficult to adequately pump sufficient samples through multiple microcosm units. A further drawback is that a single pump is used to draw water through all microcosm units, which may lead to uneven pressure displacement throughout the sampling unit and undesirable stop flow conditions. Further, known units require the use of controlled valves for each microcosm capillary, which increases complexity.
The present invention provides a system that addresses and solves the aforementioned inadequacies, while providing a flexible and cost effective sampling system with additional features. For example, in previous designs cross-communication between microcosms was not possible, while the present invention using a modular design can easily accommodate experiments or tests requiring cross-communication between test beds, where a test bed comprises a sediment-filled glass column, for example. Other benefits and advantages of the present invention will become apparent from the disclosure, claims and drawings herein.
In a further advantage over known in situ microcosm array (ISMA) systems, the present invention allows effluent from each test bed to be collected separately. In addition, larger amounts of fluid may be collected, thereby allowing chemical analysis of groundwater at heretofore unachievable, low detection limits. Known systems allowed for analysis of capillary content but not analysis of the effluent collected individually from each test bed.